Suitable transition metal complexes may be used in olefin oligomerization, involving the linking of a limited number of monomer units or in olefin polymerization wherein numerous monomer units are joined to form a polymer chain. The transition metal complexes are generally activated to perform their polymerization or oligomerization function. Activation involves, according to current theory, transformation of the neutral complex into a cation after interaction with a so-called activator.
U.S. Pat. No. 5,889,128 and WO 98/46651 describe catalysts systems suitable for living polymerizations at low temperatures (living polymerization requires the suppression of the chain termination reaction, which is most easily established at low temperatures). Polycyclic diamine ligand precursors are described in which phenyl groups are linked by a single atom oxygen bridge and nitrogen containing moieties are provided in the ortho position on the phenyl rings in which the nitrogen is directly linked to a carbon atom in the phenyl rings. In the transition metal complex the oxygen of the bridge is free to coordinate with the transition metal atom. The complex is used in conjunction with a non-coordinating anion activator, supplied in the form of the borane or a borate salt. Polymerization is started as low as −30° C.
It is among the objects of the invention to provide additional intermediates for the formation of improved ligands precursors that permit a broader range of transition-metal complexes for use in olefin polymerization. Among the objects is to provide more rigid structures with controlled amido-metal-amido angles; controlled dative interaction between a single hetero-bridging atom in the ligand and the transition metal, with improved performance at higher polymerization temperatures, especially in olefin polymerization and oligomerization, capable of providing a variety of molecular weights including an elevated molecular weight at elevated temperatures and with controlled incorporation of alpha-olefin monomers. It is furthermore among the objects to permit the synthesis of large, rigid steric ligands to reduce the symmetry of the transition metal complex and provide a bias towards stereoregular incorporation of higher alpha-olefins having at least three carbon atoms.